> One large component is that a lot of business rules and policies have been encoded into the software logic, and (re-)translating that into code in a new(er) l

> One large component is that a lot of business rules and policies have been encoded into the software logic, and (re-)translating that into code in a new(er) language is part of the challenge. It's a massive challenge. It's like a little city that has been growing for 5 decades with a new lot of houses here, a new road there, utilities routed over there, etc. Then someone saying "let's re-do this city about 10 miles that way". With a city it's easy to see the magnitude of the problem. With large software systems it's not.